Aeroelastic Coupling Modeling And Flutter Analysis Of Blades

Flutter is a self-excited instability of an elastic body coupled dynamically to fluid flowingover it. For flow velocities below critical flow speed, the fluid extracts the energy from thesystem. Small perturbations decay to zero. However, for velocities above critical value, energyfrom the flow feeds the system. Initially small oscillations dangerously grow in time.In this paper two aeroelastic systems of a single blade and two blades were modeled andvalidated. With the theories of center manifolds and normal forms, the stability of the systemswere studied in particular the bifurcations (sudden changes in the qualitative dynamic behavioras parameters change).The type of Hopf bifurcation was calculated. The influence of eachparameter on flutter speed was descripted.For a single blade in certain parameters,it is better forthe stability with a bigger mass ratio and dimensionless radius of gyration,while a smallerdimensionless location of the elastic axis aft of the leading edge.With the three parametersfixed,the flutter speed is mainly determined by dimensionless location of center of mess of bladeaft of the elastic axis and the ratio of uncoupled natural frequencies. The value of the parametersshould be chosen in reason to get a bigger flutter speed.In this paper, the aeroelastic coupling calculation results of single blade and double bladesare useful for reference on blade flutter prediction and aero-elasticity analysis.